package java50practice;

public class java21 {
	public static void main(String[] args) {
		long count=0;
		for(int i=1;i<=20;i++){
			long jc=1;
			for(int j=1;j<=i;j++){
				jc=j*jc;
			}
			count+=jc;
		}
		System.out.println(count);
	}
}
